fix(seo): Add noindex for platform and business subdomains

Dynamically set robots meta tag to noindex/nofollow when on any
subdomain (platform.*, demo.*, etc.). Only the root domain
marketing pages should be indexed.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

frontend/src/App.tsx

@@ -191,6 +191,30 @@ const AppContent: React.FC = () => {
     localStorage.setItem('darkMode', JSON.stringify(darkMode));
   }, [darkMode]);
 
+  // Set noindex/nofollow for app subdomains (platform, business subdomains)
+  // Only the root domain marketing pages should be indexed
+  React.useEffect(() => {
+    const hostname = window.location.hostname;
+    const parts = hostname.split('.');
+    const hasSubdomain = parts.length > 2 || (parts.length === 2 && parts[0] !== 'localhost');
+
+    // Check if we're on a subdomain (platform.*, demo.*, etc.)
+    const isSubdomain = hostname !== 'localhost' && hostname !== '127.0.0.1' && parts.length > 2;
+
+    if (isSubdomain) {
+      // Always noindex/nofollow on subdomains (app areas)
+      let metaRobots = document.querySelector('meta[name="robots"]');
+      if (metaRobots) {
+        metaRobots.setAttribute('content', 'noindex, nofollow');
+      } else {
+        metaRobots = document.createElement('meta');
+        metaRobots.setAttribute('name', 'robots');
+        metaRobots.setAttribute('content', 'noindex, nofollow');
+        document.head.appendChild(metaRobots);
+      }
+    }
+  }, []);
+
   // Handle tokens in URL (from login or masquerade redirect)
   React.useEffect(() => {
     const params = new URLSearchParams(window.location.search);